Designing Hierarchical Storage Systems for Interactive On-demand Video Services

1 Designing Hierarchical Storage Systems for Interactive On-Demand Video Services S.-H. Gary Chan Fouad A. Tobagi Department of Electrical Engineering Stanford University Stanford, CA 94305 Abstract|A hierarchical storage system achieves scalable storage in providing on-demand video services. In such a system, video les are stored in a tertiary level (such as a library or jukebox), and transferred to a secondary level (such as magnetic disks) from which it is streamed to the users. In this paper, we study the design of such a system for interactive applications in which a movie has to be completely transferred (or \staged") to the secondary level before it is displayed to its user; thereby incurring some user delay. We specify the required storage and bandwidth to meet a delay goal, given application characteristics. We have developed an accurate and yet simple model for the system, which greatly facilitates the design process and allows us to extract important performance characteristics of the system. We provide some design examples, and study the in uence of video popularity. Keywords|Hierarchical storage systems, interactive video services, tertiary storage, secondary storage, storage system model